Mechanical locks have been around for thousands of years, and in recent decades electronic locks have come to market and been adopted by both businesses and consumers. While electronic locks offer substantial benefits over mechanical ones, if a business or consumer wishes to install an electronic lock at an existing door or other barrier, they often must replace much if not all of the existing locking hardware. Such an approach is costly. In addition to imposing a cost burden, the decision to change hardware may force the purchaser to change the aesthetic look of the door, drawer, or other locked barrier if the lock provider or locking system provider does not support the same style or finish of the existing lock hardware. Even if a business or consumer is installing a new door or other barrier rather than retrofitting, the purchase decision will likely reflect a mix of concerns such as cost, convenience/usability, security and aesthetics. An electronic lock that is small and that can essentially act as a component of many competitive locking systems would be highly valuable in both the retrofit and new door/barrier contexts. In addition to compactness, an electronic lock that is highly energy efficient is very valuable: high power consumption typically adds manufacturing cost due to the need for a more powerful (and often, more bulky) power supply, and it increases operating costs. If the power supply is replaceable (e.g., a battery), the need to replace the power supply more frequently adds maintenance costs and is less convenient.